In studies on the bacteriophage T4 DNA polymerase (gene 43) we will study the effects of changing enzyme quantity and quality on the rate of DNA chain growth at and away from the DNA replication growing point. Amounts of enzyme will be estimated by using sensitive gel electrophoretic assays and changes in DNA structure in response to polymerase changes will be examined by sucrose gradient analysis. In studies on genetic regulation of synthesis of DNA replication enzymes we will isolate and characterize T4 mutations that specifically alter activity from certain genes. We have already isolated some such mutations. We will attempt to locate the promoter, operator, repressor and other genetic sites that control the genes responsible for nucleic acid metabolism in phage-infected E. coli.